Conventionally, for optical instrument such as an optical communication, a measuring apparatus and a semiconductor laser, use has been made of an optical device such as an etalon, a halfwave plate and a quarterwave plate.
Some of these optical devices are comprised by bonding a plurality of transparent members with each other.
For example, when explaining an optical device of an etalon, there is proposed an air gap type which is configured by bonding two transparent members (see for example Patent Literature 1).
In such an optical device, metal films for bonding are provided on the surfaces of the transparent members. The members are bonded in a state where the metal films are superimposed on each other to obtain an optical device.
Further, as the optical device, for example, there is also proposed a device formed in a state where a plurality of transparent members are bonded while forming an interior space in a path portion for transmitting the light (see for example Patent Literature 1).
Further, where an optical device configured by bonding a plurality of transparent members is produced, for example, use is made of a mask configured by a frame member, pattern portions for forming shapes of interior spaces, and arms for connecting the pattern portions and the frame member. The mask is superimposed on the transparent member. In that state, metal film is formed in the clearances of the mask.
In this case, metal film is not provided at the arm portions. Therefore, for example, recessed portions which are communicated with the outside as disclosed in Patent Literature 2 are formed.